In order to meet traffic demand of mobile data service, it is possible to densely deploy small cells in some hotspots indoor or outdoor, on the basis of conventional macro base stations cellular networks. The small cells have characteristics of small coverage, low transmission power, which are suitable for providing high speed data transmission service, performing splitting flow of data for the macro cellular networks, and reducing the network deployment cost of operators. The forms of small cells may include: multi-carrier cell (Metro cell), Micro cell, Pico cell, Femto cell, or wireless local area network (Wireless Local Area Network, WLAN) which uses wireless fidelity (Wireless Fidelity, WiFi) technology and etc., and different forms of wireless network access nodes which are used by small cells can be generally referred to as small base stations.
In order to transmit data normally, a small base station needs to be synchronized, meanwhile, the small base station also should provide downlink synchronization to user equipments (User Equipment, UE) in its cells. In the prior art, small base stations use the same configuration to transmit synchronization reference signal to realize inter-station synchronization and UE downlink synchronization. Since a small base station cannot transmit and receive at the same time at the same frequency, the synchronization reference signal, which is received by a small station, for inter-station synchronization sent by other small stations and the synchronization reference signal sent by the small station to a UE in its cell for UE downlink synchronization need to be separated by at least one transmission period of a synchronization reference signal, and when the period is relatively long, it would cost a relatively long time to achieve the inter-station synchronization and UE downlink synchronization, which undoubtedly would influence timing synchronization performance.